This invention relates to a device for atomization of fuel in combustion engines and more particularly, the atomization of fuel in combustion engines having fuel injection systems.
It has been known in the prior art to use the retrograde effect of fuel.
DE-OS 2800894 describes a process which utilizes the properties of retrograde substances. Succinctly stated, in order to convert a retrograde substance such as gasoline into the gaseous state, the substance is brought to a specific temperature and a specific initial pressure and is then reduced to a lower specific end pressure with the initial temperature being so chosen that the gasoline at the lower pressure state is in a gaseous state. These retrograde substances do not absorb heat from the general surrounding when entering the gaseous state.
The principle of the atomization or vaporization of retrograde substances by heating under high pressure in the liquid phase and subsequent adiabatic or polytropic relief of the pressure has diverse applications. The end pressure can, for example, be the chamber pressure in a combustion engine or the atmospheric pressure in a combustion chamber of a furnace.
In the case of combustion engines, it is advantageous to heat the fuel before injection into the cylinder or the prechamber of the engine.
The above referred to German OS reference also describes a system for carrying out the process, but the system proposed in this document, despite an integrated non-return valve, has the drawback of the possible formation of a vapor lock in the injection valve. Additionally, the system is not intended for dynamic, demand-responsive control of the fuel heating in accordance with the particular characteristic-dependent engine operation state, with the result that the efficiency is necessarily considerably impaired, especially in transitional states.
It has also been customary to preheat the fuel/air mixture to reduce the cold start and warm-up emissions and to improve the performance.
For example, a number of fuel mixture heating devices (early fuel evaporators) have been used, many of which use positive temperature coefficient (PTC) ceramic heaters to heat one or more metal heating elements arranged in the intake manifold of the engine. The heating elements are suffused with an atomized fuel and/or fuel/air mixture. Due to structural reasons and air flow considerations, these devices have not proved altogether satisfactory, especially in the case of multi-port injection systems. More specifically, these devices have heat exchange capacity shortcomings and cause fluid flow losses for the engine. The problem of an unavoidable fluidic mismatch of the heating device in the intake manifold necessarily results therefrom, and gives rise to a significant loss in maximum output of the engine.